Treatment of hydrocarbon oils



June 20, 1939. B. .1. FLOCK ET AL 2,163,275

' I TREATMENT OF HYDROCARBON OILS Fiied Aug. 14,1936.

FraCfioIZQfor- Faefibrzafiprfofynzer irqy tkavzberzs INVENTORS BERNARD J. FLOCK EDWI F. NELSON ATTORNEY Patented June 20, 1939 PATENT OFFICE TREATMENT OF HYDROCARBON OILS Bernard J. Flock and Edwin F. Nelson, Chicago,

111., assignors to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application August 14, 1936. Serial No. 95,996

1 Claim. (01. 196-10) This invention relates particularly to the treat ment of hydrocarbon gases produced incidental to the cracking of the heavier portions of petroleum oils for the primary object of producing gasoline, although the process is applicable also to treatment of certain gaseous hydrocarbon frac tions tobe later more fully described which are produced when cracking other heavy hydrocarbonaceous materials such as those produced in the primarydistillation of coal, lignites, shale,

etcetera.

More specifically, the invention. is concerned with a modification and an improvement in catalytic processes which are aimed at the conversion of the lower boiling and normally gaseous olefins presentin cracked products into liquids of gasoline boiling range. Owing to the generally dehydrogenating character of cracking reactions, there are considerable percentages of olefins present in all of the products of cracking from the gases down through the lighter liquids to the heavier residua. The character of the unsaturation in the total products and in the various fractions will depend upon the character of the original charging stock to the cracking process and the conditions of severity employed in respect to temperature, pressure and time of exposure to cracking conditions. This unsaturation embraces not only compounds of an open 30 chain structure but also compounds characterized by closed rings of an aromatic or hydroaromatic character.

. The unsaturated character of cracked products is generally advantageous from a standpoint of the quality. at-present most desirable in-automotive fuels, since the anti-knock value which is commonly expressed as octane number increases generally as unsaturation increases though there are various digressions from this general rule in 40 the case of isomeric or condensed structure hydrocarbons. Thepresentprocessisconcernedwith the eflicient utilization of the lower boiling olefinic products of cracking whereby they are polymerlzed by the use of selected catalytic contact 45 materials and a particular mode of operation to produce optimum yields of the polymer products which are of the highest possible anti-knock value. Owing to the requirement of a limited vapor pressure in saleable gasolines, there is gen- 50 erally an overproduction of hydrocarbons of 3 and 4 carbon atoms, and by the present process the olefinic constituents of these so-called propane-butane mixtures are utilized as a' source of additional yields of high anti-knock material which can be blended with the total gasoline products from the cracking process or with other motor fuels of inferior anti-knock value.

In one specific embodiment, the present invention comprises the polymerization of the olefins in the overhead fractions from stabilizers operat- 5 ing upon primary cracked distillates for the removal of the unnecessary excess of 3 and 4 carbon atom fractions by separately and selectively contacting the gaseous and the liquid phases from the overhead distillate receiver of the stabilizer with 10 solid phosphoric acid catalysts.

From the foregoing brief statement of the character and scope of the present process it will be obvious to those familiar with such matters that the details of operation will be capable of con- 15 siderable modifications without departing from the spirit of the invention. However, for purposes of illustration and for more accurately defining the process, the attached diagrammatic drawing has been provided which indicates'in 20 general side elevation by the use of conventional figures an arrangement of apparatus in which the process may be conducted, though it is not intended to limit the scope of the invention in exact correspondence therewith.

Referring to; the drawing, line I, containing control valve 2, is for the admissionof primary cracked naphthas which aret'o be stabilized to a given vapor pressure while utilizing the overhead light fractions as a source of olefin containing materials to be polymerized. As a rule, since substantially all cracked naphthas are condensed and collected under plant pressure, which maybe anywhere from 100 to 500 pounds per square inch, there will be relative small percentages of light gases such as hydrogen, methane, ethane, and ethylene in the primary distillates which are reheated for the stabilizing step, so that these lighter gases which are not affected by polymerizing catai'ystswill commonly be present in only 40 negligible quantities and the overhead subjected to polymerization will therefore be in a sense a concentrate of 3 and. 4 carbon olefins and possibly some heavier which are readily polymerized by the preferred catalysts.

Asa rule primary cracked distillates are stabilized at pressures of approximate 100-150 pounds per square inch and heated to approximately 225-275 F. before they are admitted to the stabilizing column, 'The top temperature may be held at approximately 100-150 F. (depending upon the percentage of low-boiling frac-- tions present) by cooling devices or the return of overhead reflux and the bottom of the tower may be held at 275-325 F. by means of indirect contact heaters or other reboiling devices to permit accurate stripping of the gasolines or naphthas. The draw line 4, containing control valve 5, permits the withdrawal of stabilized products from stabilizer 3.

The overhead fractions pass in vapor form through line 6, containing control valve 1, and are condensed during passage through a condenser 8 after which liquid and vapor fractions pass through line 9, containing control valve In, to a receiver II. In this receiver there will be a partition of liquid and vapor phases which will be due to the fact that the overhead fractions are of a.

phases varies in respect to higher olefin content and another of which is that there is an advantage in pumping liquid material particularly when the use of high pressures are desirable in subsequent polymerization, since liquid pumps are more eflicient and more easily controlled than vapor phase compressors. The separate treatment of the liquid and vapor phases therefore permits of greater flexibility and better control of the polymerization process to produce optimum yields of liquid polymers from overhead distillates from stabilizers which are commonly known as stabilizer refluxes.

Following the process as outlined in the drawing, the vapor phase from the stabilizer is picked up by a compressor 23 from line 2|, containing control valve 22, and pumped through a line, containing control valve 25, through a heating element 25 arranged to receive heat from a furnace 21 in which the vapor fractions are brought to a suitable temperature for their polymerization. With the preferred catalyst to be presently described and for the average composition of mixtures produced at this point temperatures from approximately 250-450" F. are generally most suitable and by proper manipulation of such controllable factors as pressure, time of contact and emci'ency of catalyst, the mixtures may be either selectively polymerized to remove the olefins in order of their reactivity or may be subjected to average conditions to produce separate fractions varying in physical and chemical conditions.

. According to the present process the liquid condensate in receiver ll passes through a line l2, containing control valve l3, to a pump I4, which serves the double purpose of returning a portionof the liquid to the top of the stabilizer by way of line l5, containing control valve l6, and line H, containing 'c'ontrolvalve l8, and the remaining portion which maybe designated as the make of the plant to a second catalytic polymerizing unit by way of line l9, containing control valve 20, and into a primary heater 49 disposed to receive heat from a furnace setting 50 Thev catalysts which are preferably employed to'efl'ect the polymerization of olefins in the two phases according to the present process are of. a veryspecial character and their use is considereda special feature thereof.

lysts are designated generally as solid phosphoric acid catalysts and are made by the gen,-

These cataamae'rs eral steps of mixing an acid of phosphorus (usually the ortho or the pyro acid) with a substantially non-catalytic and usually siliceous adsorbent material until a rather stiff paste is obtained and then either calcining the pasty material under controlled conditions to produce a solid cake which is ground and sized to produce catalyst I particles or which is first formed into small particles by extrusion or pelleting methods and then calcined until particles of optimum characteristics in respect to quantity and character of phosphoric acid and its condition of fixation in the particles is assured. v

In the primary mixing of phosphoric acids and adsorbents, ordinary temperatures may be employed in case the ortho acid is used but in case the pyro acid is employed, somewhat elevated .temperatures above its melting point are more suitable to insure its fluidity. Since the precalclning step in the preparation of the catalyst evidently tends to form an acid slightly over pyrephosphoric acid in respect to the degree 01' dehydration of the phosphoric anhydride, advantages in time are usually gained by starting with the pyro acid. In some instances, however, when it is desired to operate to more or less selectively polymerize and remove isobutene from cracked gas mixtures, weaker catalysts in which the or-' tho acid predominates may be better employed and it is comprised within the scope of the invention to employ this type of, precalcined catalyst. The proportions of acid and adsorbent may also be varied so that precalcined mixes in which the 'acid constitutes a minor percentage by weight may be employed or in which it con-' Some of the preferred adsorbent materialswhich may be used with the phosphoric acids are such materials as kieselguhr, bentonite clays, silica gel, and incidental materials such as the oxides of the alkaline earth metals and certain heavy metal halides such as zinc chloride which may contribute to the total efl'ectiveness oi the catalyst composites ultimately produced. Calv cining may be conducted at temperatures as high as 600 F. and if necessary or desirable the calcined mixes may be subsequently contacted with superheated steam at temperatures of the order of 450-550" F. to control the concentration of the adsorbed acid catalyst. I

In the operation upon the vapor phase from the receiver heated materials pass through line 28, containing control valve 29 and through a series of catalytic treaters typified by 30 and II in which the preferred catalysts are present as filler and in which the oleflnes in the entering mixtures are converted into liquids by polymerization. Suitable operating conditions are temperatures from 350 to 550 F. and pressures of 100 to 300 pounds per square inch. The two treaters-shown are to indicate that any suitable arrangements may be employed either in series or parallel connection and there may be if desired intermediate separation of polymers and collection of individual fractions, or the total .materi'als may be gradually polymerized during passage through a succession of treaters and polymers may be so withdrawn while the lighter portions are taken overhead as vapors or removed as a side cut.

The overhead from fractionator 36 passes through line 39, containing control valve 40, and a portion thereof is condensed during passage through a condenser 4|, the condensed liquid along with uncondensed gases and vapors following line 42, containing control valve 43, to

receiver 44 which has a fixed gas release line 45,

v a cracking plant operating upon topped crudes from Mid-Continent and West Texas fields was containing control valve 46, and a liquid draw 'line 41, containing control valve 48, which may comprise in some instances propane-butane fractions containing a suflicient quantity of olefins to make further contacting with the catlysts desirable or which may be essentially parafiinic so that they are only utilizable if subjected to dehydrogenation to produce higher percentages The liquid phase from receiver I I which has been pumped under considerable superatmospheric pressure through line 19 and valve 20 and preheated during passage through element 49 in furnace 50 willpass through a line 5|, containing control valve 52, to a separate polymerizing plant which may, as in the case of the plant operating upon the vapor phase from the receiver consist of any. suitable arrangement of polymerizing chambers typified in-the drawing by 55 and 55' which are connected by transfer line 53, containing control valve 54. Owing to the greater ease of developing high pressure in the pumping of the liquid phase, it is practical to employ conditions which favor the primary selective polymerization of isobutane to form the olefin dimer which is hydrogenatable to the isooctane designated as 2;2,4-trimethyl pentane. This may be accomplished for example by introducing the liquid mixtures at temperatures from ordinary atmospheric up to 200 F. under pressure of the order of 500-600 pounds per square inch so that the primary catalyst beds are operating upon material which is still essentially in liquid phase. By further modifying the conditions of operation, selective mixed polymerization of iso and. n-butenes may be eflected which in some cases produces ultimately the highest yields of high octane. number hydrogenated products which apparently contain high percentages of 2,2,3-trimethyl pentane. Suitable conditions for this modified operation are temperatures from 275 to 325 F., pressures of 500 to 600 pounds per square inch, and contact time of 250 to 350 seconds. A later example will indicate the commercial possibilities of this type of operation.

As indicated in the drawing, although intermediate separation of selected polymer fractions may also be practiced, the total products from the second polymerizing unit pass through line 56 containing control valve 51 and are fractionated by fractionator 58 from which liquid bottoms are withdrawn through line 59, containing control valve 60. Overhead vapors follow line 6|. containing control valve 62, and may be partially condensed by condenser 63 after which the condensed liquids and uncondensed gases pass through line 64, containing control valve 65, to a receiver 66 having a conventional gas release line 61, containing control valve 68, and a liquid draw line 69, containing control valve 10.

The foregoing general description of a characteristic operation of the process has indicated some of its alternative modes of operation which may be employed to effectively produce selected polymer fractions from the stabilizer overhead. As already indicated the description is general in respect to some of thedetails of operation in the polymerizing -units and is given merely to show the general features of the process. The following example is introduced toindicate the results obtainable by. the separate and specific treatment of the liquid and vapor phases in the stabilizer of a. cracking process. I

The overhead naphtha distillate produced in treated. The average gravity of the topped crude mixture was A. P. I. and the cracking plant pressure and a temperature of 100 F. and the following table indicates the composition of the total overhead reflux and the vapor and liquid phases, respectively, which were available for polymerizing treatment:

Composition of stabilizer overhead Percent in Percent in Percent in Component total over- "20% vapor 80% liquid head phase phase Methane 2. 9 9. 0 1. Ethylene 3. 3 6. 1 2. Ethane l3. 2 23. 4 l0. Propylene. 22; 1 l9. 8 22. Propane.. 33. 2 30. 4 33. isobutene. 4. 2 2. 5 4. Isobutane 6. 4 4. 1 7. n-butenes. 8. 4 3. 0 9. n-butane 6. 3 1. 5 7. Higher olefins 34. 7 25.3 36.

The vapor phase material from the stabilizer distillate receiver was contacted with solid phosphoric acid catalyst in a series of treating towers at a maintained average temperature 'of 425 F.

and a pressure averaging about 175 pounds to produce approximately 4 gallons of 85 octane number polymer per' 1000 cubic feet of mixture treated. This treatment of the vapor phase material was conducted without the use of a compressor to step up the pressure from that of the stabilizer reflux receiver.

Liquid phase material was pumped up to a pressure of 550 pounds per square inch and treated to produce selective polymer fractions. Inthe first treating stage the material was contacted with a solid phosphoric acid catalyst at a temperature of approximately 300 F. and for a time of contact of approximately 250 seconds.

This caused a maximum of mixed polymerization between the isobutene and the n-butenes and produced approximately 8 gallons per 1000 cubic feet of entering mixture (calculated as a gas) of liquid polymer which when substantially completely hydrogenated showedan octane num- V The overall increase in octanenumber by blending the liquid polymers 'was from approximately 68 to 70 which brought the plant product in this particular instance up to premium grade. We claim as our invention:

A process which comprises stabilizing cracked hydrocarbon distillate to remove normally gaseous hydrocarbons therefrom, subjecting the evolved gases to partial liq'uefaction to form a liquid phase of relatively high olefin content and a gaseous phase of lower olefin content, said stabilization and partial'liquefaction being effected under substantial superatmospheric pressure, supplying the liquid phase 'material, without lowering the pressure thereon, to a polymerizing zone and therein subjecting the same to catalytic polymerization in the absence of the material of said gaseous phase and under suflicient superatmospheric pressure to maintain a substantial portion thereof in liquid condition, supplying the gaseous phase material to a second polymerizing zone maintained under lower pressure than the first-named zone and subjecting the same therein to vaporphase polymerizing conditions.

BERNARD J. FLOCK. EDWIN F. NELSON. 

